The present invention relates to compounds that inhibit the enzyme aminoimidazole carboxamide ribonucleotide formyl transferase (AICARFT), to pharmaceutical compositions containing these compounds, and to their use to inhibit AICARFT. The-invention also relates to the preparation of these compounds, and to intermediates for preparing these compounds.
The large class of antiproliferative agents includes antimetabolite compounds. A particular subclass of antimetabolites known as antifolates or antifoles are antagonists of the vitamin folic acid.
Aminoimidazole carboxamide ribonucleotide formyl transferase (AICARFT) is a folate-dependent enzyme in the de novo purine biosynthesis pathway. This pathway is critical to cell division and proliferation. Shutting down this pathway is known to have an antiproliferative, in particular, an antitumor effect.
There is a need for compounds that inhibit the enzyme AICARFT, having antitumor, antiinflammatory, antipsoriatic, and/or immunosuppressive activity.
An object of the invention is to provide small-molecule compounds that inhibit AICARFT. Another object of the invention is to provide antitumor, antiinflammatory, antipsoriatic, or immunosuppressive agents useful in pharmaceutical treatments.
Surprisingly, such objects have been achieved by the compounds of formula I: 
wherein:
R1 is H or CN;
R2 is phenyl or thienyl, each of which may be optionally substituted with phenyl, phenoxy, thienyl, tetrazolyl, or 4-morpholinyl; and
R3 is phenyl substituted with xe2x80x94SO2NR5R6 or xe2x80x94NR5SO2R6 and optionally further substituted by one or more of the suitable substituents defined below; wherein R5 is H or lower alkyl, R6 is lower alkyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl, wherein the aryl and heteroaryl moieties may be substituted by one or more of the suitable substituents defined below; or 
xe2x80x83wherein n is an integer of from 1 to 4, R4 is OH, lower alkoxy, or a glutamic-acid or glutamate-ester moiety linked through the amine functional group.
The invention also relates to pharmaceutically acceptable salts, solvates, prodrugs, and active metabolites of compounds of the formula I.
In preferred embodiments, R2 is selected from 
and/or
R3 may be phenyl substituted with xe2x80x94SO2NR5R6 or xe2x80x94NR5SO2R6 and optionally further substituted by lower alkyl, lower alkoxy, or halogen. For example, R3 may be: 
each of which may be optionally substituted with one additional substituent selected from methyl, methoxy and chloro.
Perferred compounds of the invention are: 
and pharmaceutically acceptable salts, solvates, prodrugs, and active metabolites of such compounds.
The invention further relates to use of the compounds of formula I, and especially the above-described preferred compounds, as inhibitors of the enzyme AICARFT.
The invention also relates to methods of synthesizing the compounds of the invention, comprising carrying out the following general alkylation reaction: 
where R1, R2, and R3 are as defined above.
Other features, objects, and advantages of the invention will become apparent from the detailed description of the invention provided below.
In accordance with a convention used in the art,  is used in structural formulae herein to depict the bond that is the point of attachment of the moiety or substituent to the core or backbone structure.
Where chiral carbons are included in chemical structures, unless a particular orientation is depicted, both stereoisomeric forms are intended to be encompassed. Further, the inventive compounds may exist as single stereoisomers, racemates, and/or mixtures of enantiomers and/or diastereomers. All such single stereoisomers, racemates, and mixtures thereof are intended to be within the broad scope of the present invention. Preferably, however, the inventive compounds are used in optically pure form.
As generally understood by those skilled in the art, an optically pure compound is one that is essentially enantiomerically pure. Preferably, an optically pure compound of the invention contains at least 90% of a single isomer (80% enantiomeric excess), more preferably at least 95% (90% e.e.), even more preferably at least 97.5% (95% e.e.), and most preferably at least 99% (98% e.e.).
The compounds illustrated by the chemical formulae referred to herein may exhibit the phenomenon of tautomerism. Although the structural formulae depict one of the possible tautomeric forms, it should be understood that the invention nonetheless encompasses all tautomeric forms.
As used herein, the term xe2x80x9calkyl groupxe2x80x9d is intended to mean a straight- or branched-chain monovalent radical of saturated and/or unsaturated carbon atoms and hydrogen atoms, such as methyl (Me), ethyl (Et), propyl, isopropyl, butyl, isobutyl, t-butyl, ethenyl, pentenyl, butenyl, propenyl, ethynyl, butynyl, propynyl, pentynyl, hexynyl, and the like, which may be unsubstituted (i.e., containing only carbon and hydrogen) or substituted by one or more suitable substituents as defined below (e.g., one or more halogens, such as F, Cl, Br, or I, with F and Cl being preferred). A xe2x80x9clower alkyl groupxe2x80x9d is intended to mean an alkyl group having from 1 to 4 carbon atoms in its chain.
An xe2x80x9calkoxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORa, where Ra is an alkyl group. Exemplary alkoxy groups include methoxy, ethoxy, and propoxy. xe2x80x9cLower alkoxyxe2x80x9d refers to alkoxy groups wherein the alkyl portion has 1 to 4 carbon atoms.
An xe2x80x9carylxe2x80x9d group is intended to mean a cyclic aromatic hydrocarbon group, such as phenyl or naphthyl, which may be unsubstituted or substituted by one or more of the suitable substituents defined below (e.g., with one or more halogen, lower alkyl, and/or lower alkoxy group). Preferably, aryl is a substituted or unsubstituted phenyl group.
A xe2x80x9cheteroarylxe2x80x9d group is intended to mean a cyclic aromatic group containing at least one heteroatom selected from oxygen, sulfur and nitrogen, wherein any position of the heteroaryl group may be unsubstituted or substituted by a suitable substituent, as defined below (e.g., with a halogen, lower alkyl, or lower alkoxy group). Preferably the heteroaryl group is a nitrogen-containing cyclic aromatic group. Exemplary nitrogen-containing heteroaryl groups include quinolyl, isoquinolyl, indolyl, pyridyl, pyrrolyl, pyrazinyl, and thiazolyl. A xe2x80x9cheteroarylalkylxe2x80x9d group comprises an alkylenyl moiety bonded to a substituted or unsubstituted heteroaryl group, e.g., xe2x80x94(CH2)x-indolyl, wherein x may be an integer of from 1 to 4 and any position of the heteroaryl group may be unsubstituted or substituted by a suitable substituent, as defined below. Preferable heteroaryl groups include substituted or unsubstituted isoquinolyl or indolyl groups.
The term xe2x80x9csubstituentxe2x80x9d or xe2x80x9csuitable substituentxe2x80x9d is intended to mean any suitable substituent that may be recognized or selected, such as through routine testing, by those skilled in the art. Illustrative examples of suitable substituents include hydroxy groups, halogens, oxo groups, alkyl groups, acyl groups, sulfonyl groups, mercapto groups, alkylthio groups, alkoxy groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, carboxy groups, amino groups, alkylamino groups, dialkylamino groups, carbamoyl groups, aryloxy groups, heteroaryloxy groups, arylthio groups, heteroarylthio groups, and the like.
The term xe2x80x9coptionally substitutedxe2x80x9d is intended to expressly indicate that the specified group is unsubstituted or substituted with one or more suitable substituents, unless the optional substituents are expressly specified, in which case the term indicates that the group is unsubstituted or substituted with the specified substituents. As defined above, various groups may be unsubstituted or substituted (i.e., they are optionally substituted) unless indicated otherwise herein (e.g., by indicating that the specified group is unsubstituted).
A xe2x80x9cprodrugxe2x80x9d is intended to mean a compound that is converted under physiological conditions or by solvolysis or metabolically to a specified compound that is pharmaceutically active.
A xe2x80x9csolvatexe2x80x9d is intended to mean a pharmaceutically acceptable solvate form of a specified compound that retains the biological effectiveness of such compound. Examples of solvates include compounds of the invention in combination with water, isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, or ethanolamine.
A xe2x80x9cpharmaceutically active metabolitexe2x80x9d is intended to mean a pharmacologically active product produced through metabolism in the body of a specified compound.
A xe2x80x9cpharmaceutically acceptable saltxe2x80x9d is intended to mean a salt that retains the biological effectiveness of the free acids and bases of the specified compound and that is not biologically or otherwise undesirable. Examples of pharmaceutically acceptable salts include sulfates, pyrosulfates, bisulfates, sulfites, bisulfites, phosphates, monohydrogenphosphates, dihydrogenphosphates, metaphosphates, pyrophosphates, chlorides, bromides, iodides, acetates, propionates, decanoates, caprylates, acrylates, formnates, isobutyrates, caproates, heptanoates, propiolates, oxalates, malonates, succinates, suberates, sebacates, fumarates, maleates, butyne-1,4-dioates, hexyne-1,6-dioates, benzoates, chlorobenzoates, methylbenzoates, dinitrobenzoates, hydroxybenzoates, methoxybenzoates, phthalates, sulfonates, xylenesulfonates, phenylacetates, phenylpropionates, phenylbutyrates, citrates, lactates, xcex3-hydroxybutyrates, glycollates, tartrates, methane-sulfonates, propanesulfonates, naphthalene-1-sulfonates, naphthalene-2-sulfonates, mandelates, and mesylates.
If a compound is a base, a desired salt may be prepared by any suitable method known in the art, including treatment of the free base with an inorganic acid, such as hydrochloric acid; hydrobromic acid; sulfuric acid; nitric acid; phosphoric acid; and the like; or with an organic acid, such as acetic acid; maleic acid; succinic acid; mandelic acid; fumaric acid; malonic acid; pyruvic acid; oxalic acid; glycolic acid; salicylic acid; pyranosidyl acid, such as glucuronic acid or galacturonic acid; alpha-hydroxy acid, such as citric acid or tartaric acid; amino acid, such as aspartic acid or glutamic acid; aromatic acid, such as benzoic acid or cinnamic acid; sulfonic acid, such as p-toluenesulfonic acid or ethanesulfonic acid; or the like.
If a compound is an acid, a desired salt may be prepared by any suitable method known in the art, including treatment of the free acid with an inorganic or organic base, such as an amine (primary, secondary, or tertiary); an alkali metal or alkaline earth metal hydroxide; or the like. Illustrative examples of suitable salts include organic salts derived from amino acids such as glycine and arginine; ammonia; primary, secondary, and tertiary amines; and cyclic amines, such as piperidine, morpholine, and piperazine; as well as inorganic salts derived from sodium, calcium, potassium, magnesium, manganese, iron, copper, zinc, aluminum, and lithium.
In the case of compounds, salts, or solvates that are solids, it is understood by those skilled in the art that the inventive compounds, salts, and solvates may exist in different crystal forms, all of which are intended to be within the scope of the present invention and specified formulae.
The present invention is also directed to a method of inhibiting AICARFT activity, comprising contacting the enzyme with an effective amount of a compound of formula I, or a pharmaceutically acceptable salt, prodrug, pharmaceutically active metabolite, or solvate thereof. For example, AICARFT activity may be inhibited in mammalian tissue by administering a compound of formula I or a pharmaceutically acceptable salt, prodrug, pharmaceutically active metabolite, or solvate thereof. The compounds of formula I may also be used to inhibit the growth or proliferation of viruses and/or cells of higher organisms or microorganisms such as yeast, bacteria and fungi. The invention is also directed to methods of treating cancer by administering to a patient in need of such treatment an effective amount of a compound of the formula I, or a pharmaceutically acceptable salt, prodrug, pharmaceutically active metabolite, or solvate thereof.
xe2x80x9cTreatingxe2x80x9d or xe2x80x9ctreatmentxe2x80x9d is intended to mean at least the mitigation of a disease condition in a mammal, such as a human, that is mediated by the inhibition of the activity of the target (e.g., reduction in tumor growth), and includes: (a) prophylactic treatment in a mammal, particularly when the mammal is found to be predisposed to having the disease condition but not yet diagnosed as having it; (b) inhibiting the disease condition; and/or (c) alleviating, in whole or in part, the disease condition.
The potency of the inventive compounds as inhibitors of AICARFT activity may be measured by any of the suitable methods known to those skilled in the art, including in vivo and in vitro assays. An example of a suitable assay for activity measurements is the AICARFT enzyme assay described herein.
Administration of the compounds of the formula I and their pharmaceutically acceptable prodrugs, salts, active metabolites, and solvates may be performed according to any of the accepted modes of administration available to those skilled in the art. Illustrative examples of suitable modes of administration include oral, nasal, parenteral, topical, transdermal, and rectal.
An inventive compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof may be administered as a pharmaceutical composition in any pharmaceutical form recognizable to the skilled artisan as being suitable. Suitable pharmaceutical forms include solid, semisolid, liquid, or lyophilized formulations, such as tablets, powders, capsules, suppositories, suspensions, liposomes, and aerosols. Pharmaceutical compositions of the invention may also include suitable excipients, diluents, vehicles, and carriers, as well as other pharmaceutically active agents, depending upon the intended use.
Acceptable methods of preparing suitable pharmaceutical forms of the pharmaceutical compositions are known or may be routinely determined by those skilled in the art. For example, pharmaceutical preparations may be prepared following conventional techniques of the pharmaceutical chemist involving steps such as mixing, granulating, and compressing when necessary for tablet forms, or mixing, filling, and dissolving the ingredients as appropriate, to give the desired products for oral, parenteral, topical, intravaginal, intranasal, intrabronchial, intraocular, intraaural, and/or rectal administration.
Solid or liquid pharmaceutically acceptable carriers, diluents, vehicles, or excipients may be employed in the pharmaceutical compositions. Illustrative solid carriers include starch, lactose, calcium sulfate dihydrate, terra alba, sucrose, talc, gelatin, pectin, acacia, magnesium stearate, and stearic acid. Illustrative liquid carriers include syrup, peanut oil, olive oil, saline solution, and water. The carrier or diluent may include a suitable prolonged-release material, such as glyceryl monostearate or glyceryl distearate, alone or with a wax. When a liquid carrier is used, the preparation may be in the form of a syrup, elixir, emulsion, soft gelatin capsule, sterile injectable liquid (e.g., solution), or a nonaqueous or aqueous liquid suspension.
A dose of the pharmaceutical composition contains at least a therapeutically effective amount of the active compound or agent (i.e., a compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof), and preferably is made up of one or more pharmaceutical dosage units. The selected dose may be administered to a mammal, for example, a human patient, in need of treatment mediated by inhibition of AICARFT activity, by any known or suitable method of administering the dose, including topically, for example, as an ointment or cream; orally; rectally, for example, as a suppository; parenterally by injection; or continuously by intravaginal, intranasal, intrabronchial, intraaural, or intraocular infusion.
An xe2x80x9ceffective amountxe2x80x9d is intended to mean a therapeutic amount of an inventive compound that, when administered to a mammal in need of treatment, is sufficient to effect treatment for disease conditions alleviated by the inhibition of the target (i.e., AICARFT) activity, such as tumor growth. The amount of a given compound of the invention that will be therapeutically effective will vary depending upon factors such as the particular compound, the disease condition and the severity thereof, the identity of the mammal in need of treatment, which amount may be routinely determined by artisans.
An exemplary dose of a compound of the invention for a vertebrate host comprises an amount up to one gram of active compound per kilogram of the host, preferably one-half of a gram, more preferably 100 milligrams, and most preferably, about 50 milligrams or less, per kilogram of the host weight.
The pharmaceutical compositions of the invention may further comprise one or more other pharmaceutically active compounds. For example, for anticancer compositions, one of the following antitumor agents may be included: mitotic inhibitors (e.g., vinblastine); alkylating agents; dihydrofolate reductase inhibitors or thymidylate synthase inhibitors; antimetabolites (e.g., 5-fluorouracil, cytosinearabinoside); intercalating antibiotics (e.g. adriamycin, bleomycin); enyzmes (e.g., asparaginase); topoisomerase inhibitors (e.g., etoposide); and biological-response modifiers (e.g., interferon). The compositions of the invention may also comprise another enzyme inhibitor such as a GARFT inhibitor or antiproliferative agent, such as a compound described in U.S. Pat. No. 5,610,319 or U.S. Pat. No. 5,574,039, the disclosures of which are herein incorporated by reference. The compositions of the invention may also comprise one or more antibacterial, antifungal, antiparasitic, antiviral, antipsoriatic, or anticoccidial agent. Exemplary antibacterial agents include sulfonamides, such as sulfamethoxazole, sulfadiazine, sulfameter, or sulfadoxine; dihydrofolic reductase inhibitors, such as trimethoprim, bromodiaprim, or trimetrexate; penicillins; cephalosporins; and the quinolone carboxylic acids and their fused isothiazolo analogs.
The skeletal framework for the molecules of formula I may be assembled by the alkylation of the appropriate arylthiol with the corresponding alkyl bromide: 
5-[(Arylthio)alkyl]thiophene-2-carboxylic acids and the 5-[(arylthio)alkyl]theno-2-yl glutamatic acids are prepared by the base-catalyzed hydrolysis of the requisite methyl esters and diethyl esters, respectively.
6-Phenyl-2-thiouracil is a commercially available aryl thiol; the other 6-aryl-4(3H)-oxopyrimidine-2-thiols are prepared by base-catalyzed condensation of the corresponding aroylacetate with thiourea. 5-Cyano-6-[5-(2-thienyl)thien-2-yl]-4(3H)-oxopyrimidine-2-thiol is synthesized from the condensation of equimolar amounts of 2,2xe2x80x2-bithiophene-5-carboxaldehyde, thiourea, ethyl cyanoacetate, and potassium carbonate.
The alkyl bromides are prepared from their alcohol precursors by treatment with carbon tetrabromide and triphenyl phosphine. In general, the 5-(hydroxyalkyl)thiophene-2-carboxylates and the [5-(hydroxyalkyl)theno-2yl]glutamates are prepared by the palladium-catalyzed coupling of the requisite hydroxyalkyne with either methyl 5-bromothiophene-2-carboxylate or diethyl N-(5-bromotheno-2-yl)glutamate, followed by hydrogenation of the triple bond. The (hydroxymethyl)bisaryl sulfonamides are generally prepared by reduction of the corresponding methyl esters, which may be synthesized by sulfonylation of the appropriate aniline with the requisite sulfonyl chloride.